Wordnet 3.0
NOUN (1)
1. someone with an aggressively negative attitude;
Moby Thesaurus II by Grady Ward, 1.0:
40 Moby Thesaurus words for "naysayer": anomaly, bitter-ender, brawler, crosspatch, defeatist, defendant, denier, diehard, disputant, dissenter, dissentient, dissident, freak, individualist, inner-directed person, intransigent, irreconcilable, last-ditcher, litigant, misfit, negativist, nonconformist, noncooperator, objector, obstructionist, obstructive, oddball, opposer, oppositionist, pessimist, plaintiff, prophet of doom, protester, quarreler, refuser, resister, sceptic, scrapper, sport, wrangler

